A conventional mixer for an engine for mixing a fuel and air supplied to an engine is described in Japanese Utility Model publication JPH08 (1996)-002460Y2 (document 1). The mixer includes a base portion including an intake passage in which air flows, a fuel passage in which a fuel flows, and a mixing space in which the fuel flowing from the fuel passage and the air flowing from the intake passage are mixed, a fuel control valve which is provided so as to face a valve opening of the base portion and which is a needle-shape, and a drive portion for moving the fuel control valve in an axial direction. According to the document 1, as illustrated in FIG. 15, when the fuel control valve 700 of a needle shape moves in the axial direction MA thereof, a passage area of the valve opening 800 changes and a degree of opening of the fuel control valve 700 changes.
According to the document 1, as illustrated in FIG. 15, a configuration is employed in which the passage area of the valve opening 800 changes when the fuel control valve 700 of the needle shape moves in the axial direction thereof (direction of the arrow MA). Accordingly, for finely adjusting a flow rate of the fuel and increasing a fuel controllability, a degree θ1of a cone surface 701 of the fuel control valve 700 of the needle shape needs to be small and a distance of direct motion of the fuel control valve 700 of the needle shape needs to increase. However, in this case, the mixer would be upsized in the axial direction (direction of the arrow MA) of the fuel control valve 700 of the needle shape.
Further, in the mixer for an engine, there can be a danger that an end portion of the fuel control valve 700 of the needle shape contacts with a valve seat 810 because of vibrations of the engine. There can be a danger that this can cause a change of performance or formation of scratches. Accordingly, the fuel control valve 700 of the needle shape is designed so that the end portion of the fuel control valve 700 of the needle shape does not contact with the valve seat 810 of the valve opening 800 of the base portion when the degree of opening of the fuel control valve 700 is set to minimum. Accordingly, complete closing operation is difficult for the fuel control valve 700. As a result, fuel controllability was not always sufficient in a situation of a small degree of opening. Further, in a situation where a maximum passage area of the valve opening 800 is set by moving the fuel control valve 700 of the needle shape in a direction in which the fuel control valve opens, for ensuring a passage area at the maximum degree of opening of the fuel control valve 700, a diameter of the valve seat 810 needs to be upsized. In this case, though a passage area of the valve opening 800 can be ensured at the maximum degree of opening of the fuel control valve 700, a passage area of the valve opening 800 would be large at the minimum degree of opening of the fuel control valve 700. In this term also, fuel controllability in a situation of a small degree of opening of the fuel control valve 700 was not sufficient.
A need thus exists for a mixer for an engine, an air conditioning apparatus driven by an engine, and a power generation apparatus driven by an engine, which are downsized and advantageous for increasing fuel controllability and which can ensure fuel controllability at a small degree of opening of a valve. The present invention has been made in view of the above circumstances and provides such a mixer for an engine, an air conditioning apparatus driven by an engine, and a power generation apparatus driven by an engine.